Information storage devices are used to write, store, and selectively retrieve stored data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more magnetic heads that can read data, write data, or both, in conjunction with a magnetic recording medium (e.g., disk).
To perform functions of magnetically recording and reading data from a spinning magnetic disk, the magnetic head, suspended at the end of an actuator arm, must be correctly positioned over the magnetic disk surface during use, while the disk spins at a high rate of speed. The magnetic head must maintain a height (“fly height”) and orientation (e.g., in terms of pitch and roll) at all tracks of a magnetic disk across the varied radii of the magnetic disk, even though the linear velocity of the disk will be slower at inner radii and substantially faster at outer radii.
To achieve desired fly height and orientation of the magnetic head, the head relies on an “air-bearing surface” that faces the spinning magnetic recording disk surface and maintains the magnetic head at a desired elevation above the surface. The air-bearing surface is designed to work with a fluid at the disk drive interior that moves past the air-bearing surface due to the spinning movement of the hard magnetic disk. Forces produced by the moving fluid on the air-bearing surface cause the air-bearing surface to be suspended at a stable height and stable orientation relative to the spinning magnetic disk. The fluid may be air or a lower density gas such as helium or a mixture of helium with air or another gas. Note that the term “air”-bearing is used herein even if the surrounding fluid is not air, e.g., is helium or another low density gas.
The air-bearing surface contains certain structures that cause the magnetic head to be held at a desired height and with stable orientation above the spinning disk surface. The structures are designed to place pressure and to direct airflow over the air-bearing surface in ways that are useful to provide desired fly height and stability. Examples of these surface structures include structures referred to as pads (“pressure pads” and a “center pad”), channels and rails (to direct flow), transition regions, and regions of a maximum etch depth, among others.
The composition of an atmosphere in which the magnetic head will function, e.g., helium or air, is an important factor that affects performance of an air-bearing surface, and must therefore be considered in the design of an air-bearing surface. Because of the very substantial difference between the density of air and the density of helium (which is about one seventh the density of air), magnetic heads and air-bearing surfaces have been designed for use in either an air atmosphere or a helium atmosphere, but are not typically designed to be used in more than one type of atmosphere.